Multiple reactor filter section



July 12, 1949. M. MORRISON 2,475,909

I MULTIPLE REACTOR FILTER SECTION Filed Aug. 18, 1943 INIW Patented July 12, 1949 UNITED STATES PATENT OFFICE MULTIPLE macros FILTER SECTION Montford Morrison, Upper lllontclair, N. J

Application August 18 1943, Serial No. 499,104

5 Claims.

This invention relates to electrical wave-filters and has particular reference to carrier-current telegraph system filter-circuits, Where weight, size and cost are important factors.

Among the objects of my invention are; to provide a, filter circuit structure that is smaller, lighter and more compact than structures of the prior art meeting the same performance; to provide a filter structure meeting said same performance capable of lower cost of manufacture; and to provide a simple filter structure, for certain classes of work, which is easily portable, adaptable to office equipment, and practical for inter-communication systems.

These and other objects will be obvious and pointed out upon reading the specification in con" nection with the accompanying drawing, which shows a general schematic diagram of an embodiment of the invention.

In the prior art, electrical wave-filters have been constructed of sections comprising individual reactors tuned to individual condensers. In-

dividual sections may comprise more reactors than condensers, and/or they may comprise more condensers than reactors, but in any case no one reactor is tuned to more than one frequency.

I have discovered that by themultiple tuning of single reactors, a new class of filter circuits may be constructed which, for certain classes of application, are smaller, lighter, and cost less to manufacture. In this specification, no attempt will be made to completely cover all possible developments of this invention, but only sufficient teaching will be set up to enable one skilled in the art to which this invention appertains to make and use same.

The accompanying drawing is a schematic diagram of a so-called coupled-circuit filter, adapted to carrier telegraph channel separation.

The complex wave to be filtered is introduced by the complex wave generator I, which in the present case generates only frequencies which are harmonics of the 7th to the 19th order inclusive,

of a fundamental frequency.

The input coil 2 is tuned to these various harmonics by the input condensers, as illustrated in the figure, the 1th harmonic being tuned by a condenser in series with the full winding of the coil 2, as identified by the notation 7th. Likewise, the 9th harmonic it tuned with coil 2 at a tapped position on the coil with an individual condenser identified by the notation 9th; the 11th harmonic is tuned to a second tap by means of a 3rd condenser, as identified by the notation 11th; and so on, up to the 19th harmonic.

Input coil 2 is coupled to output coil 3 by some means, preferably positional with reference to flux leakage, and the output coil 3 is tuned to input 4, through a multiplicity of condensers '6, i, 8 and 9.

In this type of filter, followin the conventional method used in the art, it will be understood by tuning, that "tuning as an individual circuit is meant, and the common way to accomplish this is to have the coils, not in circuit with the actual circuit being tuned, to v be opened, as will be understood by those familiar with the art.

The procedure for tuning coils 3 and 9 is to tune to the Ythharmonic first, using condenser 9; then taps are so selectedon coils 3 and A that the combination of condensers 8 and 9 with the taps l9 and H selected tune the circuit between points l9 and 12 to the 11th harmonic, and that part of the circuit between points It and i3 simultaneously to the 17th harmonic. By a similar process, tuning is obtained for the 13th and'liith harmonic, and again, likewise similarly, tuning is obtained for the 9th and 19th harmonics between the parts of the circuit identified in the drawing.

While there are three other circuits available, identified by :13, y and z inthe figure, no use made of these. circuits'in the present embodiment.

The output coil 5 is then tuned to the 7th to the 19th, inclusive, by proper selection of taps and condensers, as will now be understood from the foregoing specification, the 7th harmonic appearing at the load resistor 14, the 9th appearing at the load resistor l5, the 11th harmonic appearing at the load resistor l5, and so on to the 19th harmonic which appears at the load resistor 29.

Such a filter has in its composite form all the desirable characteristics of a set of individual filters, and therefore, if the filter is designed such that the output circuit provides very narrow band filtering, such a filter will obviously attenuate the frequencies in between these narrow bands. If the filter is designed such that the band width of the output circuit for the individual circuit is wide, then these bands will overlap and form a very wide band pass filter which can be designed to have very constant transmission characteris" tics over the band pass range.

Obviously, the tapped filter reactors may be used in a filter section where the coupling is not accomplished directly by the reactors themselves, but all or part of the coupling may be obtained by a condenser or an arrangement of condensers, without departing from the spirit of the invention.

A large variety of combinations, modifications, extensions, and applications may be made of this disclosure without departing from the spirit of the invention, and the scope thereof is set forth in the claims hereunder.

What I claim is:

1. In an electrical filter system for separating a plurality of waves having frequency spacings from a circuit containing a composite series of such waves; a single inductive winding having current taps thereon and having a finite series of frequency spaced current waves flowing therein, a separate resistive load respectively for each of said waves, each said load having one terminal thereof connected to a common terminal of said winding, a separate capacitor for each of said waves, each said capacitor having one terminal thereof connected to one of the other of the terminals of the loads, and each capacitor connected to a different tap on said winding to selectively transmit each of said waves into its respective load.

2. In an electrical filter system for separating a plurality of waves having frequency spacings from a circuit containing a composite series of such waves, a single inductivewinding having current taps thereon and having a. finite series of frequency spaced current waves flowing therein, a separate resistive load respectively for each of said waves, each said load having one terminal thereof connected to a common terminal of said winding, a separate capacitor for each of said waves, each said capacitor having one terminal thereof connected to one of the other of the terminals of the loads, and each capacitor connected to a different tap on said winding to selectively transmit each of said waves into its respective load and to attenuate all other of said waves into said load.

3. In a band-pass filter having at least two filter-sections, a first filter-section having a coupling winding with a current tap thereon, a second filter-section having a coupling winding with a current tap thereon, said two windings being connected in series, a capacitor in series with two said windings forming one link-coupling-circuit between two said sections, and an additiona1 cal pacitor connected between two said current taps providing an additional link-coupling-circuit between said filter sections, said link-circuits forming parallel couplings between the filter-sections.

4. In a band-pass filter having at least two filter-sections, a first filter-section having a coupling winding with a current tap thereon, a second filter-section having a coupling winding with a current tap thereon, said two windings being connected in series, a capacitor in series with two said windings forming one link-coupling-circuit between two said sections, and one additional capacitor connected between two said current taps providing two additional link-coupling-circuits between said filter sections, all said link-circuits forming parallel couplings between the filter-sections.

5. In a band-pass filter having at least two filter-sections, a first filter-section hav ng a coupling winding with current taps thereon, a second filter-section having a coupling winding with current taps thereon, said two windings being connected in series, a capacitor in series with two said windings forming one link-coupling-circuit between two said sections, and additional capacitors connected individually between said current taps providing additional link-coupling-circuits between said filter sections, said link-circuits forming parallel couplings between the filter sections.

MONTFORD MORRISON.

EEEERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,446,752 Kendall Feb. 27, 1923 1,573,323 Nichols Feb. 16, 1926 1,642,389 Shea Sept. 13, 1927 1,767,245 Kolster June 24, 1930 1,924,553 Hough Aug. 29, 1933 2,002,187 Posthumus May 21, 1935 2,239,136 Wheeler Apr. 22, 1941 2,263,376 Blumlein et a1 Nov. 18, 1941 2,299,571 Dome Oct. 20, 1942 

